1. Technical Field
The present invention relates to a technology of controlling a timing of starting printing of an image on a transported recording medium based on a timing at which a mark provided in the recording medium is detected.
2. Related Art
In JP-A-2012-200976, a digital printing apparatus is described which prints an image on a rotary paper sheet by an ink jet printer while transporting (sending normally) the rotary paper sheet in the normal direction. When restarting the printing after stopping the printing, the digital printing apparatus normally sends the rotary paper sheet after transporting (sending reversely) the rotary paper sheet in the reverse direction to the normal direction, and makes the ink jet printer start the printing. In particular, the restart of the printing is controlled based on the result of detecting a plurality of timing marks which are aligned in the normal direction and are attached to the rotary paper sheet. Specifically, the number of timing marks detected by a mark sensor while reversely sending the rotary paper sheet is counted. In addition, when the normal sending of the rotary paper sheet is started for restarting the printing, the number of timing marks detected by the mark sensor is counted, and at a timing at which a counted value matches the counted value during the reverse sending, the ink jet printer starts the printing.
However, it is not necessarily easy to reliably detect the mark by the sensor through the entire period during which the reverse transport (reverse sending) and the normal transport (normal sending) are performed. This is because there is a case where some marks pass through a position separated from a detection region of the sensor, for example, since meandering of a recording medium (rotary paper sheet) is generated. Meanwhile, in the above-described method of counting the marks detected by the sensor during each of the reverse transport and the normal transport, when the sensor fails in detecting the mark during any of the reverse transport and the normal transport, it is not possible to start the printing from an appropriate position of the recording medium.